It is known to heat a raw material batch for glass production before its introduction into the glass melt. The purpose of this heating is to bind the dust-like components in said raw material batch so as to prevent the dust-like components from being carried away by the combustion gases or by the flue gases upon introduction into the melting unit, whereby the aggressiveness of these gases is increased. Furthermore, the composition of the batch is changed by the dust entrainment and, addition, the regenerators and recuperators are contaminated with dust, greatly impairing their efficiency.
A rotatable drum is known through which a raw material batch is passed and in which it is heated before its introduction into a glass melt. As the heating in this case is performed by an additional burner, this causes a high energy expenditure. In addition, there is the risk that dust-like components will still be carried away by the flue gases, changing the composition of the batch. Furthermore, this may also cause solids reactions.
Also known, from German Patent Specification No. 865,644, is a rotatable drum in which a raw material batch is heated by an electrical heating element before its introduction into the glass melt. Even if some of the disadvantages listed above are avoided by this system, there remains the requirement that a separate heat source be provided, which causes an additional energy expenditure.
Also known, from German Patent Specification No. 457,087, is a melting furnace which is designed as a rotary drum. In a first stage of the melting operation, the burning gases, which can cause damage to the raw material batch are carried away through a pipe arranged inside the drum. However, German Patent Specification No. 457,087 does not relate to a device for the thermal treatment of the raw material batch before its introduction into the glass melt but rather to a melting device which is supplied with a batch which has not been previously thermally treated.